This description relates to phase-change ink jetting.
In some kinds of ink jetting systems, the ink (sometimes called a hot melt ink) includes a dye or pigment held in a medium such as wax that is in a solid phase at room temperature. For jetting, the ink is heated to change the wax to a liquid state that can be jetted through a jetting orifice onto a substrate from an inkjet pressure chamber. Such inks can be shipped from the vendor to the place where the jetting is done in the form of a solid, easy to handle puck. For use, the puck is loaded into a chamber where it is heated to melt the wax, and the liquid ink can then be delivered along an ink pathway to the orifice and onto the substrate. Heaters (and related thermocouples for control purposes) can be provided at places along the ink pathway to keep the ink melted while jetting is going on. If the jetting system is turned off, and returns to room temperature, the ink solidifies. Later, the heaters can be used to melt the ink to permit jetting again.
Some known hot melt inks were jetted at 125° C. and at a viscosity of 20 centipoise (cps) and contained pigments. Such hot melt inks were solid at room temperature and were heated or cooled rapidly to transition back and forth between solid and liquid phases to prevent separation of the pigments from the medium. Many of the pigments were typically made from dyes reacted with polymers and then ground up into particles so that their density was low compared to titanium dioxide, for example. Carbon black, which is not a dye, has also been used as such a pigment.
It is known to force cool transparencies after printing with hot melt ink to keep the ink from crystallizing, which would impair its transparent qualities.